In a solid-state image sensor, the pixel size becomes small along with an increase in the number of pixels, and a resultant decrease in the saturated number of charges poses a problem. Japanese Patent Laid-Open No. 2010-114275 describes a solid-state image sensor that increases the saturated quantity of charges. The solid-state image sensor described in Japanese Patent Laid-Open No. 2010-114275 includes a plurality of photodiodes stacked in a semiconductor substrate, and a vertical transistor arranged in the semiconductor substrate to read out charges from the plurality of photodiodes.
The solid-state image sensor described in Japanese Patent Laid-Open No. 2010-114275 has a complex structure including the plurality of photodiodes and the vertical transistor formed in the semiconductor substrate. For this reason, a lot of steps are necessary for manufacturing, and process control for manufacturing is difficult.